Extracting curve-skeletons from digital shapes using occluding contours

Curve-skeletons are compact and semantically relevant shape descriptors, able to summarize both topology and pose of a wide range of digital objects. Most of the state-of-the-art algorithms for their computation rely on the type of geometric primitives used and sampling frequency. In this paper we introduce a formally sound and intuitive definition of curve-skeleton, then we propose a novel method for skeleton extraction that rely on the visual appearance of the shapes. To achieve this result we inspect the properties of occluding contours, showing how information about the symmetry axes of a 3D shape can be inferred by a small set of its planar projections. The proposed method is fast, insensitive to noise, capable of working with different shape representations, resolution insensitive and easy to implement

Exploring virtual prototypes using time-critical rendering techniques

Scientists at CRS4, the Center for Advanced Studies, Research and Development in Cagliari, Sardinia, Italy, have developed a time-critical rendering algorithm that relies upon a scene description in which objects are represented as multiresolution meshes. In collaboration with other European partners, this technique has been applied to the visual and collaborative exploration of large digital mock-ups.Pubblicat

Iterative stripification of a triangle mesh: focus on data structures

In this paper we describe the data structure and some implementation details of the tunneling algorithm for generating a set of triangle strips from a mesh of triangles. The algorithm uses a simple topological operation on the dual graph of the mesh, to generate an initial stripification and iteratively rearrange and decrease the number of strips. Our method is a major improvement of a proposed one originally devised for both static and continuous level-of-detail (CLOD) meshes and retains this feature. The usage of a dynamical identification strategy for the strips allows us to drastically reduce the length of the searching paths in the graph needed for the rearrangement and produce loop-free triangle strips without any further controls and post-processing, while requiring a more sophisticated implementation to manage the search and undo operations

Evaluation of User Gestures in Multi-touch Interaction: a Case Study in Pair-programming

Natural User Interfaces are often described as familiar, evocative and intuitive, predictable, based on common skills. Though unquestionable in principle, such definitions don't provide the designer with effective means to design a natural interface or evaluate a design choice vs another. Two main issues in particular are open: (i) how do we evaluate a natural interface, is there a way to measure 'naturalness'; (ii) do natural user interfaces provide a concrete advantage in terms of efficiency, with respect to more traditional interface paradigms? In this paper we discuss and compare observations of user behavior in the task of pair programming, performed at a traditional desktop versus a multi-touch table. We show how the adoption of a multi-touch user interface fosters a significant, observable and measurable, increase of nonverbal communication in general and of gestures in particular, that in turn appears related to the overall performance of the users in the task of algorithm understanding and debugging

PAVEL: Decorative Patterns with Packed Volumetric Elements

Many real-world hand-crafted objects are decorated with elements that are packed onto the object's surface and deformed to cover it as much as possible. Examples are artisanal ceramics and metal jewelry. Inspired by these objects, we present a method to enrich surfaces with packed volumetric decorations. Our algorithm works by first determining the locations in which to add the decorative elements and then removing the non-physical overlap between them while preserving the decoration volume. For the placement, we support several strategies depending on the desired overall motif. To remove the overlap, we use an approach based on implicit deformable models creating the qualitative effect of plastic warping while avoiding expensive and hard-to-control physical simulations. Our decorative elements can be used to enhance virtual surfaces, as well as 3D-printed pieces, by assembling the decorations onto real-surfaces to obtain tangible reproductions.Comment: 11 page

Discontinuous finite element visualization

The proceedings of the conferences have been published on CD since the initiative taken by Prof. G. M. Carlomagno at the Sorrento meeting allowing authors to include in their papers color, video clips and animations.The aim of this work is the study and the implementation of appropriate visualization techniques for high-order discontinuous finite element data in two and three-dimensions. In particular, we are dealing with field discontinuity and deformed cells. Such data are produced for example by chemical simulations, by fluid dynamics simulations, or, in general, anywhere high accuracy on boundary domain description is required

Tecniche di visualizzazione volumetrica di carotaggi

Technical Report 97/2

An interactive editor for curve-skeletons: SkeletonLab

Curve-skeletons are powerful shape descriptors able to provide higher level information on topology, structure and semantics of a given digital object. Their range of application is wide and encompasses computer animation, shape matching, modelling and remeshing. While a universally accepted definition of curve-skeleton is still lacking, there are currently many algorithms for the curve-skeleton computation (or skeletonization) as well as different techniques for building a mesh around a given curve-skeleton (inverse skeletonization). Despite their widespread use, automatically extracted skeletons usually need to be processed in order to be used in further stages of any pipeline, due to different requirements. We present here an advanced tool, named SkeletonLab, that provides simple interactive techniques to rapidly and automatically edit and repair curve skeletons generated using different techniques proposed in the literature, as well as handcrafting them. The aim of the tool is to allow trained practitioners to manipulate the curve-skeletons obtained with skeletonization algorithms in order to fit their specific pipelines or to explore the requirements of newly developed techniques

Smart mirror where I stand, who is the leanest in the sand?

Abstract. In this paper we introduce the Virtuoso project, which aims at creating a seamless interactive support for fitness and wellness activities in touristic resorts. The overall idea is to evaluate the current physical state of the user through a technology-enhanced mirror. We describe the state of the art technologies for building a smart mirror prototype. In addition, we compare different parameters for evaluating the user's physical state, considering the user's impact, the contact requirements and their cost. Finally we depict the planned setup and evaluation setting for the Virtuoso project

Towards integrated object-oriented Computational Fluid Dynamics environments: Interactive Domain Editor

The simulation of fluid flows around complex geometries starts to be computationally possible. Thus, it has become important to provide the Computational Fluid Dynamics (CFD) community with tools that allow easy manipulation of physical geometry and, for an efficient use of resources, interactive splitting of computational domain. We propose here an object-oriented approach to the definition of an Interactive Domain Editor (IDE). We show how this can be a kernel of an integrated environment for CFD. We finally describe the first results of a test implementation of IDE. 1 Introduction In recent years, due to the increasing power of computers, it has become feasible to simulate fluid flows in complex geometries [Kar89, Ors80]. This has introduced a new level of complexity in the field of Computational FluidDynamics (CFD): users need to be able to describe much more complex computational spaces to flow solvers; for an efficient use of computational resources the computational domains hav..